Rheostat.



i 730,644.- A PATBNTBD JUNE 91903.

" G.B.HARTHAN.

RHEOSTAT.

API'LIUATION FILED APB.. 21, 1902.

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PATENTED JUNE 9, 1903.

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C. E. HARTHAN.

RHEOSTAT.

APPLICATION FILED APB. 21, 1902.

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No. 7305644. PATENTED JUNE 9,1903.

` C. E. HARTHAN.

RHEOSTAT.

APPLICATION FILED APB. 21, 1902. xo mmm. 4 'SHEETS-SHEET 4.

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UNITED STATES' 'Patented .fune 9, 1903.

PATENT OFFICE.

CHARLES E. HARTHAN, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

SPECIFICATION forming part f Lette-rs Patent No. 730,644, dated .T une9, 1903.

Application filed April 21,- 1902.

To @ZZ whom t may concern:

Be it known that I, CHARLES E. HARTHAN, a citizen of the United States,residing at Lynn, in the county of Essex, State of Massachusetts, haveinvented certain new and useful Improvements in Rheostats, of which thefollowing is a specification.

This invention relates to apparatus for regulating an electric current;and its object is v 1o to afford a simple easily-constructed device ofthis character which is not costly to manufacture, is eflicient inoperation, can be easily adjusted, is durable, and is well safeguardedagainst short circuits and overheating, and l5 is composed of similarunits, which enable it to be made of any desired size by duplicatingsaid units.

The invention consists of a rheostat composed of two concentric layersof wire wound 2o on blocks of insulating material, such as p0rcelain,mounted on a strong` light metal frame and housed in a sheet-metalcasing.

The features of novelty will appear in the detailed description whichfollows and in the z5 appended claims.

In the accompanying drawings, Figure l is a front elevation of myimproved rheostat with the casing partly broken away. Fig. 2.

is a cross-section on the line 2 2, Fig. l. Fig.

3o 3 is a vertical section on the line 3 3, Fig. 2. Fig. 1i is avertical section on the line a 4, Fig. 3. Fig. 5 is a similar section ofa shorter rheostat. Fig. (3 is a top plan view with the hood removed.Figs. 7 and S show the blocks 3 5 which support the wire. Fig. 9 is aplan view of the upper head, and Fig. lO is a side elevation showing amodified hood. The metal frame of the rheostat is composed of twospider-heads connected by a cen- 4o tral standard and a side'rod. Theupper head has a circular rim l, a center 2, and arms 3, connecting therim and center. The lower head is similarly constructed, but has anoffset bracket 4f cast integral with it for supporting the apparatusclear of the wall to. which the bracket is secured. A standard 5,preferably tubular for the sake of lightness and ventilation, connectsthe centers of the two heads, which stand one above the other 5o inparallel planes. At a point in the rim, preferably on the opposite sidefrom the serial No. 103.896. (No model.)

bracket, a rod 6 extends from one head to the other and is securelyfastened by a nut 8. The lower end of the rod depends below the lowerhead and is perforated and provided with a set-screw 9, so that itserves as a binding-post for one of the circuit-terminals, the otherterminal leading to a binding-post '7.

Grouped around the central standard are a plurality of blocks 10, ofinsulating material, 6o preferably porcelain. The adjacent edges of theblocks are radial to the standard and preferably abut,so that the blocksare held against angular displacement. The inner edge4 of each block isconcave and its outer edge con- Vex, the curves being preferably both ofthe same radius. As this radius is preferably greater than that of thestandard 5, in order not to give too sharp a curve to the outer edge ofthe block the inner edge willv touch the 7o standard only at its middle;but this failure to iit the standards snugly is of no consequence solong as the radial edges of the blocks abut. The blocks engage at topand bottom with ribs on the heads, and in order to be able to put two ormore blocks in line when a tall rheostat is to be built upit ispreferred to make each block with a tongue ll at one end and a groove l2at the other adapted to fit the tongue on an adjacent block, as shown inFig. 8o a. One of the heads has two parallel radial ribs I3 to receivethe tongue l1, and the other head a single radial rib la to enter thegroove 12, whereby the blocks are held securely in place.

The outer curved edges of the blocks have a plurality of transversegrooves l5 to properly space the wire 16 when it is wound upon them. Ifmore than one layer of wire is wanted,a second series of blocks can beplaced 9o outside the iirst, the curve of the inner edge of each outerblock fitting snugly on the outer edge of the inner block, against whichit is placed. If two series of blocks are used, the wire is led from onebinding-post, as 7, to and around the inner series, and when that iswound full the second series is laid in place and the wire is carriedout and around said second series until it is, full. The end of the wireis then secured to the lower end of rod 6. 10o

Vhen the rheostat is so tall as to require two or more blocks to beplaced end to end, I preby a raised conical roof 27.

fer to make them in two lengths, as shown in Figs. 7 and 8, and toarrange them so that those in one tier break joints with those inadjacent tiers, as shown in Fig. 3. rIhese units can be combined in avariety of ways to produce rheostats of any desired size.

On the side rod 6 is a slide 17, having two arms, one of which, 18,bears against the outer layer of wire. The other arm, 19, carries asetscrew 20, which bears against a copper contacteshoe 21, slidingloosely on the side rod, and presses it closely against the wire. Bymoving the slide 17 up or down the rod the successive convolutions ofwire in the outer layer are cut out or in. As the length-of wire in theouter layer is greater than that composing the inner layer, it is thuspossible to cut out more than half the resistance by moving the slide 17to the top of the side rod.

A sheet-metal casing 22'incloses the wire coils, the rod, and slide. Bysetting the coils eccentrically to the circular casing the latter willbe of a minimum size. A hood 23 is supported on the casing by braces 24,leaving` an opening for the escape of hot air, the spiderlikeconstruction of the heads, the tubular standard, and the open spacesbetween the blocks and the Wire affording a free circulation to keep theapparatus cool. In exposed situations the simple dome-shaped hood 23 maybe replaced by one composed of an annular cone 25 and central chimney26, covered This will effectually prevent rain or snow from driving intothe casing. The offset bracket 4 provides for such a space between thecasing and a supporting-wall 28 that no additional insulation isnecessary.

Vhat I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. A rheostat comprising spider-heads and a central standard, blocksor". insulating material grouped around said standard and secured inplace between said heads, and resistance-wire wound on said blocks.

2. A rheostat comprising spider-heads and a central standard, blocks ofinsulating material grouped around said standard with radial edges incontact, and wire wound on said blocks.

3. A rheostat comprising spider-heads and a central standard, blocks ofinsulating material having curved inner and outer edges and groupedaround said standard, and wire wound on said blocks.

4. A rheostat comprising spider-heads and a central standard, blocks ofinsulating material having curved outer edges provided with transversegrooves vand grouped around said standard, and wire Wound on saidblocks.

5. A rheostat comprising spider-heads and a central standard, blocks ofinsulating material having inner and outer edges curved on the sameradius and grouped around said standard, wire wound on said blocks, anouter series of similar blocks placed against the inner series, and wirewound on said outer series.

6. A rheostat in which the Wire-supporting blocks are all alike and iitupon each other edgewise and endwise.

7 A rheostat in which the wire-supporting blocks all have inner concaveand outer con- Vex edges curved on the same radius, a tongue at one endand a corresponding groove at the other end.

8. A rheostat comprising insulating-blocks having a-tongue at one endand a groove at the other end, and supporting-heads having ribs toengage with said tongue and groove.

9. A rheostat comprising a coil of wire, a rod parallel therewith, aslide on said rod, a set-'screw in said slide, and a metal shoe betweenthe set-screw and the wire.

10. A rheostat comprising a coil of wire, a rod adjacent to said coil, aslide having one arm bearing against the wire and the other carrying aset-screw, and a metal contact-shoe between said screw and the wire.

11. A rheostat comprising a coil of wire and a casing eccentric to saidcoil.

12. A rheostat comprising a head carrying the coils of wire and providedwith an offset bracket.

In witness whereof I have hereunto set my hand this 18th day of April,1902.

CHARLES E. HARTHAN.

Vitnesses:

DUGALD McK. McKILLoP, JOHN J WALKER.

